Heat transfer system and method

ABSTRACT

A heat transfer system is provided having an air-cooled heat exchanger system. The heat exchanger system has an evaporator, condenser, compressor and a fan for forcing air over a heat exchange surface for effecting heat transfer. A mist generator having at least one nozzle directs a stream of fine mist or atomized liquid coolant into the air. The mist generator is coupled to a supply of liquid coolant. A controller controls the degree of mist or atomized coolant generated by the mist generator. A filter element positioned between the at least one nozzle and the heat exchange surface captures droplets of liquid coolant. The at least one nozzle is spaced apart from the filter element for directing the stream directly into the air surrounding the filter element.

TECHNICAL FIELD

The invention relates generally to air-cooled heat transfer devices andmethods of using such devices.

BACKGROUND

Evaporative cooling has been known for centuries and is well understood.And evaporative or “swamp” coolers for the home and business have beenavailable for many decades. Mechanical refrigeration with its manyadvantages over evaporative coolers in moderate to humid climates hasbeen understood and improved upon since the beginning of the lastcentury.

Recently the particular advantages of combining evaporative cooling withmechanical cooling, and more specifically with air-cooled condensers,have been disclosed. Air conditioners that reject heat throughair-cooled condensers are inherently less energy efficient than theirlarger counterparts that reject heat to a body of water or to condenserwater and cooling towers. This advantage of water cooled over air cooledhas to do with the thermodynamics or energy transfer of waterevaporation compared to convective heat or energy transfer from theair-cooled condenser.

The unfortunate reality of the air-cooled condensing units found on mostcommercial buildings and almost all residences is that the hotter theoutdoor temperature gets the less cooling capacity the unit can provideand the more electricity it will consume. The cooling capacity decreaseis approximately linear with rising outdoor temperature. And sinceenergy consumption increase is also roughly linear, theefficiency-cooling capacity divided by energy input-is hit doubly hard.

Evaporating a stream or mist of water into the airflow through thecondenser is an effective means to reduce the temperature of thatairflow and greatly improve the heat transfer from the refrigerantthrough the condenser to the cooler airflow. The evaporation increasesthe relative humidity of the airflow through the condenser coils, but itis of no consequence since it remains outside. There is a net increasein the consumption of water compared to the water that is typically usedin the generation of electricity. However, the environmental benefitsand fuel savings weigh heavily in favor of widespread adoption of thetechnology.

Numerous inventors have observed these advantages and have disclosedtheir ideas in the prior art. Most would improve the operatingefficiency of the condensing unit initially at least, but they suffervarious shortcomings.

Gingold et al (U.S. Pat. No. 4,028,906) discloses a misting or fogginginvention that runs whenever the compressor in the condensing unit runs.It uses a fogging nozzle that sprays the water mist directly into thecondenser airflow. Gingold recognizes the need to protect the condensercoil from the scaling or build-up of calcium carbonate and otherminerals and shows an inline detergent dispenser. It is not likely thatthis would prove to be an effective inhibitor. In the best circumstanceit would add operating cost and detergent would either accumulate orrun-off. And water spray or mist at all operating conditions is notwarranted since the maximum benefit is achieved during the hottestconditions.

Welker et al (U.S. Pat. No. 4,685,308) improves upon Gingold's inventionby adding temperature sensitive response and thereby limiting mistingoperation to periods of time when it will be most effective. While thisreduces the overall water quantity used and also the scaling, he stillincludes an inline filter to reduce the scale build-up. Welker alsoraises the possibility of using a reverse osmosis filter to removeminerals. This is quite effective, but costly for the flowrates requiredand labor intensive to install. It would only be economically attractivewhere there are other required uses for the filtered water or undercritical circumstances.

Manno (U.S. Pat. No. 4,212,172) discloses a different approach thateliminates the need for inline water filters. Instead of misting orspraying the water directly onto the coils, he discloses a box withwater vanes and filters. This has proved to be effective at stopping thewater mist from reaching the condenser coils. Manno's filter unit,however, is a relatively complex open box attached by screws to thecondensing unit. The unit utilizes an internal arrangement wherein wateris directed over water vanes to create a waterfall through whichturbulent air passes before reaching the filter. The system is morecomplicated than need be, and therefore more expensive than necessary.And its configuration requires multiple units for two, three, and foursided condenser coil units. It can also be expected to increase theairflow resistance or pressure drop across the coil. This will reducethe total airflow and increase the condenser fan power consumption. Thiswill decrease the benefits of the water evaporation.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying figures, in which:

FIG. 1 is a schematic of a heat transfer system;

FIG. 2 a is a top plan view of a condenser unit employing an air-cooledsubsystem;

FIG. 2 b is a side elevational view of the condenser of FIG. 2 a;

FIG. 3 a is an elevational view of a mister post having a support stand;

FIG. 3 b is an elevational view of a mister post having a support stake;

FIG. 3 c is a top plan view of mister post;

FIG. 4 is a top plan view of a condenser unit employing a stand-offfilter assembly;

FIG. 5 illustrates a multiport regulator and controller;

FIG. 6 a is a top plan view of a condenser unit utilizing a housing witha filter element;

FIG. 6 b is a side elevational view of the condenser unit and housing ofFIG. 6 a;

FIG. 7 a is a side elevational view of a condenser unit employing afilter rack; and

FIG. 7 b is a top plan view of the condenser unit of FIG. 7 a.

DETAILED DESCRIPTION

Referring to the schematic of FIG. 1, a heat transfer system 10 isshown. The system 10 may include an air-cooled heat exchanger unit 11 inthe form of an air conditioning or heat pump unit for both residentialand commercial applications. Such units may include an evaporator 12, acompressor 14 and a condenser 15 or condensing unit 16 within a closedsystem containing a refrigerant. The units also may include a fan orblower 18 for forcing air over the condenser 15. Air conditioners andheat pumps and their operation are well known in the art. Heat pumps aresimilar to air-conditioning-only units, but may provide both heating andcooling by reversing system refrigerant flow, such as through areversing valve, to provide the desired heating or cooling operation.

The heat transfer system 10 may be a unitary system, such as acommercial rooftop unit, comprised of both condensing unit 16 andevaporator 12. Alternatively, it may be a split system with condensingunit 16 located outdoors and the evaporator indoors.

Referring to FIGS. 2 a and 2 b, the condensing unit 16, typicallylocated outdoors for air conditioners, is shown with the fan 18, whichdraws ambient or outdoor air through a condenser coil 20. In airconditioning operations, heat from the air conditioned space is rejectedto this outside air flow where it is discharged up through the fanopening 22. In the embodiment shown, the coil 20 is arranged in agenerally square or rectangular configuration 20, extending fully alongthree generally planar sides and partially along the planar fourth side.The condenser coil 20 may have other configurations as well, such as acircular or oval shape, with the configurations having planar andnon-planar shaped sides. As used herein, the expression “non-planar” ismeant to encompass both curved shapes and the combination of two or moreplanar shapes that are non-coplanar, such as may be formed by angled orperpendicular planes. The portion 24 of the condensing unit 20 that doesnot have a coil may be occupied by the compressor, power supply (notshown) and other components for the system 10.

The heat transfer system 10 includes an air-cooling subsystem 26(FIG. 1) for cooling the air used with the air conditioning or heatexchanger unit 11. The subsystem 26 includes a liquid coolant flowregulator 28. A controller 30 is coupled to the regulator 28. Theregulator 28 has a liquid coolant inlet 32 and a liquid coolant outlet34. The regulator 28 may include a valve 36, which may be a solenoidvalve or other operable flow regulating device or valve to regulate theflow of liquid coolant from inlet 32 to outlet 34. The valve 36 may be asimple on/off valve, or it may be variable or adjustable to regulate thedegree of flow therethrough.

The liquid coolant is typically water, although the invention may haveapplication to systems that may employ other coolants as well. The watermay be supplied from a variety of sources. For residential applications,however, the water may be supplied from an externally-located faucet orspigot associated with the home or dwelling utilizing the system 10, forconnection to a garden hose or the like. Indeed, the inlets and outlets32, 34 may be provided with threaded couplings sized and configured forconnection to conventional garden hoses and the like.

The liquid coolant source may also include non-potable water. This mayinclude collected rainwater, water from an open reservoir (egs. lakes,ponds, etc.) or gray water. Gray water is typically water waste fromsinks, showers, bathtubs, but typically not from urinals and toilets.This non-potable water is finding more frequent use thanks tosustainability movements such as the U.S. Green Building Council's“Leadership in Energy and Environmental Design” (LEED) program. Thewater may be filtered and used for irrigation, sometimes to flushtoilets, and other uses where potable water is not required. Thenon-potable water may be filtered, if necessary, and pumped for use inthe present invention.

The controller 30 may include a control or logic board, microprocessoror other device, which may be programmed or configured to providevarious control and monitoring functions as described herein. Thesubsystem 26 may be powered through an electrical connection, such as aconventional power cord 38, which may be configured for coupling to apower outlet, such as 120V, provided with the associated building ordwelling. Alternatively, the subsystem components may be hardwiredseparately or with the components of the heat exchanger unit 11. Thesubsystem 26 may also be provided with a battery power source.

The controller 30 may have various sensors 40, 42 (FIG. 1) for detectingand monitoring ambient and system conditions. These may include but arenot limited to sensors for detecting and monitoring whether the unit 11or condenser unit 16 is running or off, sensors for monitoring theoutdoor or ambient dry-bulb and wet-bulb temperatures (from whichoutdoor relative humidity can be determined) or humidity, the length oftime the compressor 14 has been running, the current drawn by thecompressor 14 or the entire unit 11, the compressor discharge pressure,the liquid refrigerant temperature, or whether a power providing entityor other entity has provided a signal or instruction, such as forelectricity demand curtailment, which is discussed in more detail lateron.

Because the liquid refrigerant temperature of the unit 11 is directlyrelated to the compressor pressure, which in turn is determined by theoutdoor temperature, it could be used as a single measure of how hardthe condensing unit is working and whether air cooling by the subsystem26 is necessary. The controller output or response to these inputs wouldthen be utilized to activate or adjust the degree of air cooling by thesubsystem 26.

The controller 30, particularly when used with heat pumps, may have thecapability of locking out or halting the misting operation, such as whenthe outdoor temperature is below 70° F. (adjustable). This would ensurethat no mist would flow when the unit is operating in heating mode orwhen little advantage is derived from such misting.

Water may be supplied to the inlet 32 through a flexible hose 52, suchas a length of garden hose, connected to a faucet or spigot associatedwith the house or dwelling (not shown). Water may also be suppliedthrough a dedicated water line, which may be a flexible or non-flexibleconduit. After the water passes through the regulator 28, it dischargesthrough the outlet 34 and into a distribution conduit or hose 54. Thishose conveys the water to a first mister post 60, which may be a rigidconduit or pipe. Since the water flow rate may be quite low, about 8 to15 gallons per hour, more typically 10 to 12 gallons per hour, on atypical 5-ton residential air conditioning unit, a single hose may beadequate to supply all of the mister posts.

Alternatively, the controller may have a manifold or multiplexer thatsupplies water to two or more individual hoses: one hose to each misterpost. And if the regulator 28 is equipped with multiple solenoid valves,this method can be used to stage the misting at the condensing unit, asis discussed later on. If the staging of mist is not required, then themultiplexing can also be achieved with the use of a flow splitter ormanifold on the hose 54 or outlet 34 downstream of the regulator 28.

The regulator 28 and/or controller 30 may be positioned on the ground orsupport surface adjacent to the condenser unit 16 or they may be mountedto the condensing unit 16 for a more orderly installation. Thedistribution hoses 52, 54 coupled to the inlets and outlets 32, 34 maybe allowed to rest on the ground or other surrounding support surface,such as a rooftop.

In the embodiment shown in FIGS. 2 a and 2 b, there are four misterposts 60 that are spaced apart about the perimeter of the condensingunit 16. These are shown in a generally upright or vertical orientationand generally spaced outward from, but generally proximate to thecorners of the unit 16, which is shown having a generally squareconfiguration. Other locations for the mister posts 60 could be used, aswell. The posts 60 may be connected to the water supply via flexiblelengths of hose 54 having couplings such as those of a garden hose orthe like. This allows the user flexibility in selecting the location ofthe hoses with respect not only the condensing unit 16, but also tofences, walls, landscaping, other condensing units, and other obstacleslocated around or surrounding area to the condensing unit 16. The postsmay be located approximately 6 to 24 inches, more typically 12 to 16inches, from the condensing unit to maximize the amount of mistevaporation, but this distance may be varied to account for wind orother factors.

The mister posts 60 are shown in more detail in FIGS. 3 a-3 c. FIGS. 3aand 3 b show two side views of mister posts 60 a, 60 b, respectively.Both posts 60 a, 60 b constitute rigid conduits that may be formed froma variety of different materials, such as copper, PVC, etc. PVC or othermaterials used for the mister posts 60 that may be subject todegradation from ultraviolet radiation or from prolonged outdoorexposure may be painted or treated to resist such degradation. Althoughthe mister posts 60 are shown as being generally straight or linear inshape, they may have non-linear shapes as well. The posts 60 may be of alength so that they coextend or substantially coextend with the heightof the condenser unit 16.

The mister posts 60 may be provided with a different support or mountingstructure 62 depending upon the environment in which it is to be used.The supports 62 may be non-fixed so that the posts 60 may be moved andrepositioned at selected locations, if desired. As shown in FIG. 3 a,the post 60 a is provided with a support or stand 62 a for use on agenerally non-penetrable surface, such as a rooftop or concrete areas,so that the post 62 a may be held in a generally upright manner. In theembodiment shown, a tripod stand is used. If necessary, the support 62 amay be bolted or otherwise secured or fastened to such surface or to thecondensing unit 16 or other fixture.

As shown in FIG. 3 b, the support 62 b of the post 60 b is in the formof a stake that may be inserted into the ground or other penetrablesurface. This may be useful in residential condensing units that areoften surrounded by grass or landscaping. Note that on commercial roofs,it is often a rooftop unit-comprised of both the condensing unit andrefrigerant evaporator unit-that is installed. In this case the tripodmount 62 a would still work well. Either of the mounts 62 a, 62 b may besecured to the post 60 by a securing device 63.

The posts 60 may also be fastened or mounted directly to the condensingunit 16 or heat exchange unit 11, if desired.

Each post 60 may be provided with a hose connection 64 having an inlet66 and outlet 68. In the embodiment shown, the hose connection 64 islocated at the lower end. Coupled to the inlet 66 and outlet 68 of eachpost 60 is a length of the flexible hose or conduit 54 which joins theoutlet 68 to the inlet of the next adjacent post 60. In the case of thelast post 60 (FIG. 2 a) located furthest downstream, the second oroutlet hose connection 68 can be capped off to prevent flowtherethrough.

Located along the length of each post 60 are one or more mister nozzles70. As shown in the embodiment of FIGS. 3 a-3 c, two or more sets ofmister nozzles 70 are provided, each set being longitudinally spaced adistance from the other along the length of the post 60. The nozzles 70of each set may be directed in different directions on generallyopposite sides of the post 60 to produce a larger area of mist oratomized spray into the air. The nozzles may be directed into the airslightly away and not directly towards the condenser coil. Thisincreases the effective travel path of the mist, which begins toevaporate and adiabatically cool the condenser airflow. Most of the mistis entrained into the airflow moving toward the condenser coil. Thenozzles may be oriented so that the mist pattern does not come intocontact with any structure where collecting or condensation of the mistmay occur. The nozzles may provide a spray of fine mist or atomizedwater that is readily evaporated in the air immediately surrounding thefilter element, as is discussed later on. Nozzles with a flow capacityof 0.3 to 0.7 gph, more typically around 0.5 gph, at typical waterpressures are effective at producing a suitable atomized mist.

FIG. 3 c shows a mister post 60 with a mister plug 72 used in place ofthe mister nozzle 70. The mister plug or plugs 72 may be used ininstances where the condensing unit 16 does not have coil 20 on one sideof the post 60 or where less mist is desired. They would also be usefulin humid climates where maximum misting is not needed. The misternozzles 70 and plugs 72 may be provided with threaded connections forcoupling to corresponding connections on the post 60 to allow easyinterchange or replacement, such as when the nozzles become clogged byscale or other debris.

Referring to FIGS. 2 a and 2 b, a non-framed flexible filter element 80is provided to serve as a barrier to any unevaporated water mistdischarged from the mister posts 60. As used herein, the expression“non-framed” may encompass both a flexible filter material without anyframing structure or that may employ some type of framing structure butthat is capable of flexing with the filter material to conform tonon-planar shapes, as defined herein. The filter element may be formedfrom a layer or layers of woven or non-woven fiber material, such asthose commonly used within the indoor air handling unit of airconditioning systems. Typically, such filters utilize a randomlyoriented fiber pattern, although a non-random fiber pattern may be usedas well. A variety of different materials may be used for the filterelement, both natural and synthetic. Examples of filter material includefiberglass and polymeric materials, such as polypropylene, polyester,etc. The filter materials may be provided with or treated to provide anelectrostatic charge, such as those used to attract dust particles. Thethickness of the filter element may vary, but a thickness of from about½ to 4 inches or more may be suitable, with from about 1 to about 2inches being more typical. The filters may have a MERV rating of from 1to about 12. Examples of suitable commercially available filter materialproducts includes AMERGLAS™ Hammock Fiberglass Filter and PUROLATER™Basic Efficiency Filter Media, both fiberglass and polymeric, availablefrom Clarcor, Inc. Such materials may be supplied on rolls and cut tosize and shape.

The flexibility of the filter element 80 allows it to conform tosubstantially all non-planar shapes of existing condensing units: round,oval, square, rectangular, etc. The filter element may be a continuous,single piece of material. And it can be easily trimmed with scissors tofit the variable height and perimeter of condenser coils. When the unitis on, the airflow itself may facilitate holding the filter in placeagainst the condensing unit. Testing has shown that the overall airflowmay be reduced less than five percent by the filter. The filter may beheld in place without the use of a frame or housing structure. Thefilter element 80 may be held in place by brackets or clips 82 or otherfastening devices. Alternatively, or in addition, the filter element maybe held in place by the straps 84 or other securing devices that mayextend around the perimeter of the condensing unit 16. The straps 84 maybe provided with a fastening device, such as Velcro or hook and loopfastener or such as those used on self-locking cable ties.

Referring to FIG. 2 a, the condenser coil 20 of the condensing unit 16may be substantially covered by the flexible filter 80, which is shownwrapped around the sidewalls of the unit. As shown, the filter 80overlays the entire length and width of the condenser coil 20. Thefilter may exhibit a strong attraction to the unevaporated water due tosurface energy differences. The mist may have a strong tendency to “wet”the filter fibers. This natural attraction may be enhanced furtherthrough the use of filters with an electrostatic charge or an activeelectrostatic filter.

Referring to FIG. 2 b, a drain channel 90 is shown for collecting liquidwater dripping from the bottom of the filter 80. Although, the inventionmay minimize wasted water, some liquid water may collect, such as attimes when the outdoor relative humidity is high. This overflow may bedischarged through a drain pipe 92 to a selected location. For units inwhich the misting waterflow may be regulated, a sensor may be added nearthe inlet to drain pipe 92. When heavy run-off is indicated by thesensor, the controller 30 may actuate the regulator 28 to reduce or haltmisting.

In use, the condenser fan 12 creates a horizontal airflow from theexterior sides of the condensing unit 16 towards the condenser coil 20and discharges the air vertically up from the unit 16 through opening22. This constant airflow captures or entrains the atomized water mistfrom the misting nozzles 62 of posts 60. The misting nozzles 62 maydirect a fine mist or atomized water directly into the air without theuse or contacting of water vanes or other structures through whichturbulent air is passed prior to entering the filter assembly andcondenser coil. As the mist flows towards the condensing unit, themajority of it evaporates, lowering the dry-bulb temperature. Theportion of the mist that does not evaporate preferably should not reachthe condenser coil because it usually contains calcium carbonate, alsocalled limescale, and various other minerals. The limescale inparticular would, after extensive use, coat the coil and decrease theheat transfer from the hot refrigerant gas to the airflow. Over time thedecrease in heat transfer from the scale buildup would offset the heattransfer improvement from the mist and evaporation.

FIG. 4 show the top view of another embodiment of the basic condensingunit 16 with multiple filter stand-offs 86. These may be used tophysically separate the filter 80 from the coil 20, providing an air gapand eliminate or reduce the possibility of the unevaporated water fromthe misters contacting the coil 20. The stand-offs 86 may also increasethe total surface area of the filter 80.

FIG. 5 provides a detail view of a multi-port regulator 93, which may beused in place of the single-port regulator 28 on a single condensingunit, as described previously, or with multiple condensing units. Theregulator 93 may be operated by means of the controller 30. In thisparticular embodiment, the regulator 93 has two or more valves 94, whichmay be solenoid valves or the like, for either staged misting on asingle condensing unit or for on-off misting on multiple condensingunits. This can be especially useful for larger individual residenceswith two or more condensing units located in the same area. It wouldalso be useful for commercial buildings or apartments with severalcondensing units located in a given area. With multiple units, eachdischarge hose can serve the mister posts (not shown) for a given unit.For staged misting on a single unit, each outlet conduit 54 could supplya single post or a pair of posts.

The regulator 93 is also shown with a freeze-prevention feature. A drainor bleed valve assembly 96 may be provided with the multiple conduits ofthe regulator 93. Each conduit may be provided with its own drain valveassembly 96 having a valve 98 that may be normally closed, but upon lossof power or on freeze conditions is opened to allow the water in themister posts and hoses drain out. For additional protection a dribblevalve assembly 100 having a valve 102 can also be added on the watersupply side. Under freeze conditions the valve 102 opens allowing just asmall amount of water to drip out to prevent freezing. In regions offrequent hard freezes, it may be desirable to shut down and drain theentire system before cold weather arrives. The valve assemblies 96, 100may be opened manually or actuated automatically by the controller 30upon detected system or environmental conditions or upon instructioninput.

FIGS. 6 a and 6 b illustrate yet another embodiment of an air-coolingsubsystem that utilizes a housing 106. The housing 106, which may formpart of the filter assembly, may be rigid sheet metal, plastic or othermaterial, can be used to facilitate smoothing the airflow downstream ofthe filter material and to provide rectangular filter racks 108 to allowthe user to install standard size, rectangular framed filters 110. Theframe of such filters 110 is typically formed from cardboard, plastic orsimilar material, and may include a wire or plastic support or guardoverlaying the filter material layer. Such framed filters are readilyknown in the art for use with both residential and commercial airconditioning and heating units and are typically planar in shape andtypically have a thickness of about ½ to 2 inches, although this mayvary. The filter material used for the framed filters may be that orsimilar to that described for the filter element 80. The filters may beaccordion-type filters, as well. Suitable commercially available framedfilters include STRATADENSITY Premium Fiberglass Air Filters andDIRTDEMON Ultrastatic Pleated Air Filter. Six framed filters 110 areshown in FIG. 6 a, but could be varied in number and sized to minimizepressure drop across the filters.

The shell or housing 106 may include a channel and drain 112 forcollecting and draining unevaporated water from the filters 110. Theembodiment of FIGS. 6 a, 6 b also employs a mister nozzle assembly 114that may utilize hard-plumbed piping or conduit 116 instead of theflexible hoses and misting posts. The mister nozzle assembly 114 may bemounted or secured to the housing 106. The nozzle assembly 114 is shownfurther employing a multiport regulator 93 for staged misting. As shown,one valve of the regulator 93 controls coolant flow to a middledistribution pipe 116 and the other valve is connected to the upper andthe lower distribution pipes 118. This configuration allows threedifferent stages of misting: egs. 33%, 67%, or 100%.

FIGS. 7 a and 7 b show still another embodiment employing the condensingunit 16 with a condenser coil 20. Around the coil 20 is provided a wiremesh filter rack 120, which forms part of the filter assembly. Thefilter rack 120 may be formed from two spaced apart, parallel layers ofwire mesh 122, 124. The layers 122, 124 are spaced apart to receiveeither a non-framed or framed filter element. The wire mesh may havelarge openings and may be similar to the wire guard that is commonlyemployed on condensing units 16 to protect the coil 20 from physicaldamage. The two layers 122, 124 of wire mesh form an opening or slot 126for the filter element, which is shown removed. The filter element maybe inserted into the opening 126 from the side or top. The filter rack120 may be held in place by brackets or fasteners 128 to the condensingunit 16.

As previously discussed, the controller 30 (FIG. 1) may be provided withvarious sensors 40, 42 for monitoring ambient conditions and systemconditions. The monitored conditions, which may be one or more or acombination of such conditions, when they reach a preselected level, maycause the controller 30 to automatically start or stop mistingoperations to facilitate cooling of the air for use with the heatexchange unit 11. Additionally, the controller 30 may be used to adjustthe degree of misting, including starting and stopping of the misting,so that light or heavy mist may be provided. This may be accomplished byregulating the degree of coolant flow through a single stage mister orby using staged misting, as discussed previously.

The air-cooling subsystems described herein may also be controlledeither locally or remotely on the premises or from a remote, off-premiselocation. Such remote, off-premise control for air-cooling subsystemshas been described previously in copending U.S. patent application No.10/999,507, filed Nov. 29, 2004, which is a continuation of U.S. patentapplication No. 10/360,136, filed Feb. 7, 2003, now U.S. Pat. Ser. No.6,823,684, which claims the benefit of U.S. Provisional PatentApplication No. 60/354,979, filed Feb. 8, 2002, each of which isincorporated by reference in its entirety for all purposes.

Input or commands to the controller may be provided from such local orremote locations, such as from a home owner or dweller, buildingmanager, power providing entity, including an electric company or powerregulating entity, etc. Such input or commands may be provided locallyor remotely, such as through a wire or wireless connection, which may beconnected to a computer or other system. Two-way communication with thecontroller and the remote system may be provided.

In one embodiment, a power company, independent system operator or otherpower providing or regulating entity, could remotely actuate theair-cooling subsystem. This may be part of an implemented demandresponse management program. Such management may occur during peakelectricity demand periods during high temperature days or hours.Incentives, such as rebates, reduced rates, credits or other financialsavings may be provided by the entity to users of the air-coolingsubsystem. In addition to turning off lights and other appliances,residential and commercial users may have the option of turning on theair-cooling subsystem to decrease power consumption in response to analert or curtailment notice provided by the entities. The controllerused with the subsystem may provide a signal or otherwise communicatewith the remote location to indicate the user is eligible for suchparticipation.

The controller may also receive real-time or dynamic electricity pricinginput from a remote, off-site entity via a wire or a wireless connectionto smart interval data recorder (IDR) electric meters. These meters arebecoming more prevalent in regions where wholesale electricity pricesfluctuate widely.

The invention allows smaller air conditioning units to be used for agiven building or dwelling. Without the air-cooling subsystem, largerunits are required to match the heat gain on the very hottest day thatcan reasonably be expected. This oversizing of the air conditioning unitfor the majority of conditions may shorten the air conditioning cycle.This shorter air conditioning cycle may lead to significantly higherindoor humidity, which can facilitate mold growth. Also, shorter cycletime with more frequent starting and stopping increases wear and tear onthe air conditioning unit. Smaller units would also allow more efficientcooling and reduce costs.

While the invention has been shown in only some of its forms, it shouldbe apparent to those skilled in the art that it is not so limited, butis susceptible to various changes and modifications without departingfrom the scope of the invention. Accordingly, it is appropriate that theappended claims be construed broadly and in a manner consistent with thescope of the invention.

1. A heat transfer system comprising: an air-cooled heat exchangersystem having an evaporator, condenser, compressor and a fan for forcingair over a heat exchange surface for effecting heat transfer; a mistgenerator having at least one nozzle for directing a stream of fine mistor atomized liquid coolant into the air, the mist generator beingcoupled to a supply of liquid coolant; a controller for controlling thedegree of mist or atomized coolant generated by the mist generator; anda fiberglass filter element positioned between the at least one nozzleand the heat exchange surface for capturing droplets of liquid coolant,the at least one nozzle being spaced apart from the filter element fordirecting the stream directly into the air surrounding the filterelement, and wherein the controller includes a liquid sensor for sensingdrainage of liquid coolant from the filter element, the controlleradjusting the degree of mist or atomized liquid coolant generated by themist generator in response to a preselected drainage of liquid coolant.2. A method of transferring heat comprising; providing an air-cooledheat exchanger system having a heat rejection section and a fan fordirecting air over a heat exchange surface for effecting heat transfer;providing a mist generator having at least one nozzle for directing astream of fine mist or atomized liquid coolant into the air, the mistgenerator being coupled to a supply of liquid coolant; controlling thedegree of mist or atomized coolant generated by the mist generator witha controller; and positioning a fiberglass filter element between the atleast one nozzle and the heat exchange surface for capturing droplets ofliquid coolant, the at least one nozzle being spaced apart from thefilter element; and directing the stream of mist or atomized liquidcoolant directly into the air surrounding the filter element without theuse of water vanes, and wherein the controller includes a liquid sensorfor sensing drainage of liquid coolant from the filter element, thecontroller adjusting the degree of mist or atomized liquid coolantgenerated by the mist generator in response to a preselected drainage ofliquid coolant.
 3. A heat transfer system comprising: an air-cooled heatexchanger system having an evaporator, condenser, compressor and a fanfor forcing air over a heat exchange surface for effecting heattransfer; a mist generator having at least one nozzle for directing astream of fine mist or atomized liquid coolant into the air, the mistgenerator being coupled to a supply of liquid coolant; a controller forcontrolling the degree of mist or atomized coolant generated by the mistgenerator; and a filter element positioned between the at least onenozzle and the heat exchange surface for capturing droplets of liquidcoolant, the at least one nozzle being spaced apart from the filterelement for directing the stream directly into the air surrounding thefilter element; and wherein the controller includes a liquid sensor forsensing drainage of liquid coolant from the filter element, thecontroller adjusting the degree of mist or atomized liquid coolantgenerated by the mist generator in response to a preselected drainage ofliquid coolant.
 4. The heat transfer system of claim 3, wherein: thefilter element is flexible so that the filter element is conformable tonon-planar shapes of the heat exchanger or heat exchange surface.
 5. Theheat transfer system of claim 3, further comprising: filter racks forreceiving the filter element; and wherein the filter element is a framedfilter element.
 6. The heat transfer system of claim 3, wherein: thereare at least two conduits spaced apart about the perimeter of the heatexchanger, each conduit being supported by a non-fixed support so thatthe conduits may be positioned at selected locations.
 7. The heattransfer system of claim 3, wherein: the controller includes sensors forsensing at least one of ambient and system conditions and wherein thecontroller controls the mist generator in response to a sensed conditionreaching a preselected level.
 8. The heat transfer system of claim 3,wherein: the controller is operable from a remote, off-premise location.9. The heat transfer system of claim 8, wherein: the controller is anon-premise controller and includes sensors for sensing at least one ofambient and system conditions and communicates such conditions to anoff-premise location.
 10. The heat transfer system of claim 3, wherein:the filter element utilizes an electrostatic charge.
 11. The heattransfer system of claim 3, wherein: the mist generator is provided witha drainage valve for draining liquid coolant therefrom; and wherein thecontroller actuates the drainage valve.
 12. The heat transfer system ofclaim 3, wherein: the mist generator is a staged generator that providesat least first and second staged operations wherein the level of mist oratomized liquid coolant generated in the first staged operation isdifferent from that of the second staged operation.
 13. A method oftransferring heat comprising; providing an air-cooled heat exchangersystem having a heat rejection section and a fan for directing air overa heat exchange surface for effecting heat transfer; providing a mistgenerator having at least one nozzle for directing a stream of fine mistor atomized liquid coolant into the air, the mist generator beingcoupled to a supply of liquid coolant; controlling the degree of mist oratomized coolant generated by the mist generator with a controller; andpositioning a filter element between the at least one nozzle and theheat exchange surface for capturing droplets of liquid coolant, the atleast one nozzle being spaced apart from the filter element; anddirecting the stream of mist or atomized liquid coolant directly intothe air surrounding the filter element without the use of water vanes;and wherein the controller includes a liquid sensor for sensing drainageof liquid coolant from the filter element, the controller adjusting thedegree of mist or atomized liquid coolant generated by the mistgenerator in response to a preselected drainage of liquid coolant. 14.The method of claim 13, wherein: the mist generator includes at leasttwo conduits spaced apart about the perimeter of the heat exchanger,each conduit having one or more nozzles and being supported by anon-fixed support so that the conduits may be positioned at selectedlocations about the perimeter.
 15. The method of claim 13, wherein: thecontroller includes sensors for sensing at least one of ambient andsystem conditions and wherein the controller controls the mist generatorin response to a sensed condition reaching a preselected level.
 16. Themethod of claim 13, wherein: the controller is operable from a remote,off-premise location.
 17. The method of claim 16, wherein: thecontroller is an on-premise controller and includes sensors for sensingat least one of ambient and system conditions and communicates suchconditions to an off-premise location.
 18. The method of claim 13,wherein: the controller operates the mist generator based uponreal-time, recent cost, day-ahead or dynamic cost information relatingto water or electrical power.
 19. The method of claim 13, wherein: theliquid coolant is non-potable water.
 20. The method of claim 13,wherein: the controller is an on-premise controller that communicateswith an off-premise power providing entity to identify a user associatedwith the heat transfer system.
 21. The method of claim 13, wherein: thefilter element is flexible and conforms to a non-planar shape of theheat transfer surface.
 22. The method of claim 13, wherein: positioningthe filter element includes providing a filter rack for receiving thefilter element, the filter element being a framed filter element, andwherein the filter element is adjacent to the heat exchange surface whenreceived therein.